1. Field of the Invention
The present invention relates generally to internal combustion engines, and more particularly to, a method of controlling engine torque output of an internal combustion engine.
2. Description of the Related Art
Generally, to enhance torque output performance of an internal combustion engine, a multi-cylinder engine is designed with a "tuned" intake manifold (air induction system). Tuning is accomplished by matching induction system design parameters (runner lengths and diameters, plenum volumes, etc.) to create charge air pressure pulse peaks (a wave dynamics phenomenon) near the cylinder intake valves at certain engine "tuning" speeds. These charge air pressure pulse peaks near the cylinder intake valves cause more charge air to be inducted into the cylinder when the intake valves are open. The induction system can be designed to perform tuning at one mid range speed (first order system) or at two separate speeds (second order system).
Accordingly, there is a need in the art to switch the induction system between a first and second order system so that tuning is achieved across a wider engine speed band, resulting in a higher overall engine torque output curve. There is also a need in the art to include anticipatory functions to account for inherent time delays between an engine controller switching of a vacuum solenoid that controls an intake manifold tuning valve (MTV) and the actual valve closing or opening. Further, there is a need in the art to switch the intake MTV at precisely equal engine torque levels for a first and second order system to prevent perceivable engine performance degradation.